Alternating current sensitive relay



2 4 /m l m l M F fl M 1| 0,

Jan. 31, 1967 F. MAYER I ALTERNATING CURRENT SENSITIVE RELAY Filed Nov. 12, 1963 United States Patent 7 Claims. ((11. 335-94 This invention concerns as extremely sensitive alternating current operated relay which forms a part of an energy integrating system. The principle of increasing the sensitivity of a relay through the magnetic polarization of a magnetic circuit by a permanent field is wellknown. This principle has been successfully applied to cause the triggering of alternating current relays, but without ever attaining a sensitivity of better than or mw. in a device which is subjected to reasonable loads and vibration levels.

In order to arrive at still greater sensitivities, it is necessary, from a purely mechanical point of view, to no longer utilize the instantaneously available power, but

rather to obtain, through the storage of energy, triggering power which is substantially higher than that which is instantaneously available. To this end, there have already been suggested relays using accumulated electrical energy which, as a result, permit the attainment of a sensitivity of 0.5 to 1 mva. or better, when appropriate elements are used.

The present invention has for its object an alternating current relay adapted to effect an accumulation of the available power in order to achieve, after this integration, a discharge for producing a forceful mechanical triggering.

One relay according to this invention comprises a magnetic circuit equipped with an electrical excitation circuit adapted to conduct an alternating detector current, a resonator coupled to the magnetic circuit and tuned to the frequency of the current, capturing means responsive to a predetermined minimum input signal, or threshold, level and adapted to capture the energy accumulated in the resonator when the amplitude of its vibrations exceeds the predetermined signal level, and a trigger adapted to be activated by the energy thus captured.

-At the time of the application of a very weak electric signal to the excitation circuit of such a relay, the resonator begins to vibrate at it resonant frequency with a constantly increasing amplitude. When a certain amplitude is reached, an abrupt discharge occurs through the capturing means, which discharge then causes the trigger to come into action and to produce a triggering action at the required energy level when supplied by an appropriate source.

The characteristics and advantages of this invention will appear more clearly from the following description when taken together with the attached drawings, in which:

FIGURE 1 is a partly pictorial, cross-sectional View of a sensitive relay of the polarized type according to the invention;

FIGURE 2 is a circuit diagram of a sensing relay according to the present invention using an electronic resonator;

FIGURE 3 indicates the growth of the amplitudes of the electrical and mechanical vibrations in the devices of FIGURES 1 and 2, respectively;

FIGURE 4 is a partly pictorial, cross-sectional view of a sensing relay according to the present invention of the magnetostrictive bi-rnetallic blade type;

FIGURE 5 is a partly schematic, cross-sectional view of a differential current relay according to the present invention;

FIGURE 6 is a partly schematic, cross-sectional view of an over-voltage relay according to the present invention; and

FIGURE 7 is a partly schematic, cross-sectional view of a frequency sensing relay according to the present invention.

FIGURE 1 shows a permanently polarized relay in which a vibrating blade 1, which is made of a magnetic metal and which is tuned to the frequency of the detector current to which its is to respond, has one end rigidly fastened in a heavy base 2 which also constitutes the magnetic circuit of the unit. This circuit is polarized by the permanent magnet 3, which can be arranged in numerous ways (e.g., on the sides of base 2, in two halves, etc.), according to the standard techniques for constructing polarized relays or direct current torque motors. This magnet produces a permanent flux from the left-hand half to the right-hand half of the magnetic circuit, through both the upper and lower cross-members thereof. Because of the symmetries of the magnetic circuit reluctances, i.e., because the same mmf exists in the magnetic circuit at points opposite both ends of blade 1, none of the flux traverses the blade which, consequently, remains motionless. A detector current applied to the winding 4 causes an alternating flux to pass through the blade and to cause the blade to begin vibrating in synchronism with the current alternations.

For a given alternating current level, a force is applied to the blade during each current half-cycle, at each alternation, which force can be represented by the equation:

F =the polarization flux delivered by magnet 3 in maxwells F =the alternating flux induced by winding 4 in maxwells S=the surface of the pole-pieces in cm.

from which one can derive, by substituting the expressions representing the fluxes and by considering that the polarizing flux is much greater than the alternating flux, the following equation showing that the force is proportional to the current amplitude:

F -N-I -sin wt Force (dynes) =0.1

where:

Consequently, since it is desired to give the relay a high sensitivity the following conditions should be created: a large permanent magnetic flux; a small air gap between the blade and the magnetic circuit; a high permeability for the magnetic materials by using, for example, certain ferronickels; and a high flux concentration in the blade through a proper shaping of the pole-pieces.

The above-mentioned force will attract the free end of blade 1 first toward one pole-piece of the upper cross member of magnetic circuit 2 during one detector current half-cycle and then toward the other pole-piece thereof during the succeeding half cycle. Since this alternation of the flexing of blade 1 occurs at its resonant frequency, each successive cycle of the detector current will act to increase the amplitude of the vibration of the blade. As a result, this vibration stores, in the form of mechanical energy, the weak electrical power furnished having a small cross-section.

in a manner analogous to the result produced by an electric oscillating circuit.

When a certain vibration amplitude has been reached (for example 1 to 3 mm.) the blade will enter into the field of influence of a small magnet 5 producing a field The blade is then attracted sharply by this small magnet with a force which may reach, at the end of the deflection travel of the blade, several hundred grams. As it approaches magnet 5, the blade 1 actuates a mechanical triggering system 6 which can be of any well-known type and which is armed to trigger the opening or closing of several power control contacts 7 through the action of the force produced by the release of the tensed spring 8.

FIGURE 2 shows a diagram of one form of analogous electrical device made according to the present invention. The power delivered by an electrical voltage, which corresponds to the control signal applied across terminals 9 excites an oscillating tank circuit 10 through an inductive coupling provided by an autotransformer. Tank circuit 10 is designed to resonate at the frequency of the voltage applied across terminals 9. A second circuit, connected across the output of oscillator 10, comprises a threshold detector and energy capturing device 11 comprising, for example an npnp diode, and the coil 12 of an ordinary triggering relay. When an AC. voltage is applied across terminals 9, an alternating voltage is induced in tank circuit 10. The voltage in tank circuit 10 increases in amplitude during each half-cycle of oscillation, this voltage rapidly becoming many times larger than the voltage across terminals 9. It thus results that the power available at the output of circuit 10 may become as much as 100 to 1000 times greater than the instantaneous power available across terminals 9. When the Voltage across circuit 10 reaches the threshold level of the element 11, the latter becomes conductive and permits a powerful aperiodic discharge of the energy stored in circuit 10 through the triggering relay coil 12.

FIGURE 3(a) indicates the growth of the mechanical oscillations of the relay blade 1 of FIGURE 1, and FIG- URE 3(1)) indicates the growth of the electrical voltage in the circuit 10 of FIGURE 2. Starting from the instant t when the excitation power is applied, blade 1 begins vibrating at a constantly increasing amplitude. When a certain threshold amplitude A is reached at time t there is obtained, as indicated at 13, an attraction of the blade by the pulling or capturing magnet 5 to pull the blade to a position M situated at a distance d from the rest position of the blade. Similarly, in the device of FIGURE 2, the triggering of the diode 11 is obtained when a certain voltage level is reached, producing an aperiodic discharge through the relay 12, as indicated at 14 on FIGURE 3(b). It may thus been seen that the operation of the electromechanical device is completely analogous to that of the purely electrical device.

In order to give an idea as to the sensitivity which can be obtained with the devices of the present invention, some data will be given of the results of tests carried out with a blade having a Q (quality factor) of around 600. A power input of 0.5 mva. was found to be sufiicient for obtaining, within approximately 1 second, a vibration amplitude of 1 to 2 millimeters at 50 cycles. In other words, the blade was able to store enough energy to deliver approximately 100 times the instantaneous power applied to winding 4. With an input power of 0.02 mva., a blade vibration having an amplitude of the order of millimeters was obtained in 8 seconds, which amplitude was sufficient to cause the blade to be drawn to the capturing magnet 5. It may thus been seen that it is possible to obtain an enormous power gain with the devices of the present invention.

In order to reset the unit of FIGURE 1, it is suflicient to pull back the magnet 5 for an instant, for example, the travel of the blade 1 being limited by the pushing rod of the trigger 6, in order to permit blade 1 to return to its neutral position. Spring 8 may then be placed again in tension and trigger 6 may be manually reset. In the analogous electrical system, the npnp diode returns itself to an olf state when the discharge current reaches a sufficiently small value.

FIGURE 4 shows one embodiment of a sensitive relay according to the invention of the type employing a bimetallic magnetostrict-ive blade, which embodiment constitutes one possible modification of the embodiment of FIGURE 1. This device contains elements which are similar to those shown in FIGURE 1, with the exception that the blade 1a is a magnetostrictive bimetal which is mechanically tuned to resonate at the frequency of the excitation signal applied to winding 4a. The alternation of the direction of the alternating flux through the blade produces a variation in length (through magnetostricti-on) which has a different value for each of the two different metals, so that a deflexion is produced. It is additionally possible to provide a magnet for applying a polarization flux to the magnetic circuit.

FIGURE 5 shows one embodiment of a differential sensitive relay, constituting one type of application for the devices previously described. The terminals 15 feed a utilization device 16 through a differential toroid 1-7, the toroid feeding a relay 18 which controls a circuit breaker 19. In case of a disequilibrium in the voltage in the two lines feeding the toroid 17, through an accidental grounding of a conductor feeding one of the terminals 15, for example, a differential flux appears which actuates the relay 18, causing the relay to then disconnect the installation 16 through the opening of circuit breaker 19. The-re is thus easily obtained with a relay-triggerin g system which is both robust and insensible to shocks, a differential current sensitivity of 10 ma. The toroid '17 is of very simple construction, being for-med of only a few turns. It would even be possible to achieve a further simplification by placing all of the differential input windings directly on the coil of the relay 18.

FIGURE 6 shows one embodiment of an over-current relay. The electrical excitation is produced by a voltage transformer 26 the secondary of which is connected to two diodes 27, of silicon for example, in series with the exciting winding. Excitation is only initiated when there is a peak voltage of 0.5 or 0.6 volt because this level must be attained before diodes 27 will conduct. The device thus provides an extremely good stability with respect to the current level at which the installation will be disconnected. Such an embodiment is, contrary to the situation with thermal bi-metallic blades, practically insensitive to temperature variation (below C.) At the same time, because the relay '18 operates on the principle of energy accumulation, a relatively long triggering time passes before triggering when the desired current level is exceeded by a small amount. In other words, this arrangement combines the desirable characteristics of both thermal and magnetic circuit breakers.

In the same manner, over-voltage relays can be produced by utilising Zener diodes and by placing the excitation input in parallel across the power supply. Any other non-linear element or element with abrupt voltage characteristic (such as a saturated magnetic circuit, a tunneldiode, etc.) can also be used.

FIGURE 7 shows one form of highly sensitive relay having an extremely good frequency selectivity. The example chosen corresponds to a remote control signalling or command device placed across the power supply 15, which device may be used for example, in a private home. A signal having a very low power level and having a predetermined audio frequency (200 to 2000 cycles/sec.) is applied across terminals 15 and is subjected to a first frequency selection by a series resonant circuit 28. The signal is then subjected to a second frequency selection by the tuning of the vibrating blade 1, all frequencies outside of the resonant frequency range of this blade being ineffective for producing a triggering action. One is able to thus trigger, for example, a civilian air raid warning signal in a home, or even to alter the connections of a water heater for night rates. Utilizing several frequencies, with one such device being provided for each frequency, a telemeter can be created. By making interconnections (not shown) between the output contacts 7, and by using several devices tuned to different frequencies, one can produce true paging systems to call selected stations or to make multiple remote control commands.

It is evident that in place of the vibrating blade, one can use any other mechanical resonator, a torsional type for example. In addition, one can replace the permanent magnets with DC. actuated solenoids, etc. The various applications of which FIGURES 5 to 7 are examples, can, naturally, be made, on the other hand, by suitable adaptations of the electrical embodiment of FIGURE 2. Although the device of FIGURE 2 is shown as being excited by the control signal 9 through the intermediary of a magnetic coupling, one can also use direct or capacitive coupling to the inductance in circuit 10. The voltage produced across circuit 10, and consequently the final power amplification, is directly proportional to the circuit Q factor. One can use more complicated resonant circuits, such as coupled circuits, and even use devices having combined electrical and magnetic resonator characteristics.

It will be understood that the above description of the present invention is susceptible to various modifications,

changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What I claim is:

1. An alternating current sensitive relay comprising:

(a) a magnetic circuit;

(b) electrical excitation means associated with said magnetic circuit for inducing flux variations therein and having an input for receiving an alternating electrical excitation current;

(c) a resonator constituted by a mechanical vibrating element electromagnetically coupled to said magnetic circuit and tuned to resonate at a predetermined frequency under the influence of flux variations produced in said magnetic circuit by the excitation current for storing a portion of the energy supplied to said magnetic circuit by said excitation means, said storage being in the form of continuously increasing mechanical oscillations and said vibrating element being made of a magnetic material and forming a flux path with said magnetic circuit;

((1) capturing means including a permanent magnet disposed in the path of travel of said vibrating element and having a dimensionally small field which is substantially independent of the flux path defined by said magnetic circuit for attracting and holding said vibrating element when the amplitude of its oscillations has passed a predetermined minimum level; and (e) a mechanical trigger unit associated with said resonator to be activated by said vibrating element when said latter element has been thus attracted by said capturing means.

2. A relay as recited in claim 1 wherein said input for said excitation means comprises a differential toroid whereby the operation of said relay is dilferential in nature.

3. A relay as recited in claim '1 wherein said input for said excitation means comprises a non-linear threshold detector whereby said relay has an input threshold level which must be attained before the device will begin to operate.

4. A relay as recited in claim 1 wherein said input for said excitation means comprises a tuned electronic filter which is tuned to pass signals having a frequency equal to the resonant frequency of said resonator.

5. A device as recited in claim 1 further comprising means for causing a permanent magnetic flux to circulate in said magnetic circuit.

6. A device as recited in claim 1 wherein said mechanical vibrating element is in the form of a vibrating blade.

'7. A device as recited in claim 1 wherein said mechanical vibrating element is a magnetostrictive bi-metallic blade.

References Cited by the Examiner UNITED STATES PATENTS 1,205,731 9/ 1916 Gerdien 9-40 2,120,985 6/ 193 8 Melhose 200- 2,475,148 7/ 1949 Massa.

2,486,394 1.1/ 1949 'Eannarino 200--90 2,980,841 4/ 1961 Bearinger 3212 3,135,896 6/ 1964 Carter.

3,187,225 6/1965 Mayer 31727 X FOREIGN PATENTS 1,294,445 4/ 1962 France. 1,326,673 '3 1963 'France.

691,080 4/ 1940 Germany.

MILTON O. HIRSHFIELD, Primary Examiner.

SAMUEL BERNSTEIN, Examiner.

I. A. SILVERMAN, Assistant Examiner. 

1. AN ALTERNATING CURRENT SENSITIVE RELAY COMPRISING: (A) A MAGNETIC CIRCUIT; (B) ELECTRICAL EXCITATION MEANS ASSOCIATED WITH SAID MAGNETIC CIRCUIT FOR INDUCING FLUX VARIATIONS THEREIN AND HAVING AN INPUT FOR RECEIVING AN ALTERNATING ELECTRICAL EXCITATION CURRENT; (C) A RESONATOR CONSTITUTED BY A MECHANICAL VIBRATING ELEMENT ELECTROMAGNETICALLY COUPLED TO SAID MAGNETIC CIRCUIT AND TUNED TO RESONATE AT A PREDETERMINED FREQUENCY UNDER THE INFLUENCE OF FLUX VARIATIONS PRODUCED IN SAID MAGNETIC CIRCUIT BY THE EXCITATION CURRENT FOR STORING A PORTION OF THE ENERGY SUPPLIED TO SAID MAGNETIC CIRCUIT BY SAID EXCITATION MEANS, SAID STORAGE BEING IN THE FORM OF CONTINUOUSLY INCREASING MECHANICAL OSCILLATIONS AND SAID VIBRATING ELEMENT BEING MADE OF A MAGNETIC MATERIAL AND FORMING A FLUX PATH WITH SAID MAGNETIC CIRCUIT; (D) CAPTURING MEANS INCLUDING A PERMANENT MAGNET DISPOSED IN THE PATH OF TRAVEL OF SAID VIBRATING ELEMENT AND HAVING A DIMENSIONALLY SMALL FIELD WHICH IS SUBSTANTIALLY INDEPENDENT OF THE FLUX PATH DEFINED BY SAID MAGNETIC CIRCUIT FOR ATTRACTING AND HOLDING SAID VIBRATING ELEMENT WHEN THE AMPLITUDE OF ITS OSCILLATIONS HAS PASSED A PREDETERMINED MINIMUM LEVEL; AND (E) A MECHANICAL TRIGGER UNIT ASSOCIATED WITH SAID RESONATOR TO BE ACTIVATED BY SAID VIBRATING ELEMENT WHEN SAID LATTER ELEMENT HAS BEEN THUS ATTRACTED BY SAID CAPTURING MEANS. 